This chapter introduces two techniques for documenting business processes- Data Flow Diagrams (DFD's) and System Flowcharting (SFC). It discusses how to read these documents, their purpose, and guidelines for creating DFD's and SFC's from narratives (see discussion)
Data Flow Diagrams:
--graphical representation of a system
--depicts a system's components, the data flows among the components, and the sources, destinations, and storage of data http://spot.colorado.edu/~kozar/DFDtechnique.html This is a great page I found explaining DFD's
--here are some more web sites, which describe the elements of the DFD and the steps to drawing the DFD: http://www.compapp.dcu.ie/~renaat/ca2/ca214/ca214v.htmlhttp://www.stc.org/confproceed/2000/PDFs/00098.PDF
--Here is another one that describes the "layering" of DFD's graphically: http://www.umsl.edu/~sauter/analysis/dfd/dfd_intro.html
--Here is an example of the importance and practicality of DFD's in our society. This link shows the system process of Al-Qaida when planning the 9/11 attacks. It makes you think that if knowledge of the plot could have been found through this analysis, that maybe shutting down a link of this process could have prevented its occurrence.
Here is the PDF:
Types of Dataflow Diagrams (define and explain the differences):
Logical Data Flow Diagram -- graphical representation of a system showing the systems processes, data stores, and the flows of data into and out of the processes and data stores
Data Stores -- represent a place in the process where data comes to rest. A DFD does not say anything about the relative timing of the processes, so a data store might be a place to accumulate data over a year for the annual accounting process
Logical DFD tells what activities are being accomplished but not ho
Physical DFD - graphical represtantaion of a system showing the systems;s internal and external entities and the flows of data into and out of these entities - where, how and by whom - but not what activities are being accomplished
Physical DFD Vs Logical DFD
Physical DFD like the name says describes the physical components that perform the function where Logical explains what functions are being performed
Physical DFD: System's infrastructure. Shows how the system will be implemented including the hardware, software, files, and people involved. It conatins information about the computerized system.
Logical DFD: System's activities. Focuses on the business and how the business operates. It is not concerned with how the system will be constructed. It describes the business events that take place and the data required and produced by each event. It conatins information about the business.
Context -- top level or least detailed level--shows the data flows into and out of the system.
External Entities--those entities outside the system that send or receive data from the system
Level-0 -- will have the same number of data flows to external entities as the context level (level balancing). It also describes the overall processing of the system by showing one process for each major processing step or functional requirement.
Level-1 -- A continuation of Level 0 where, as necessary, the steps of the major processes are shown.
Level-x (How low can you go?) The general principle in Data Flow Diagramming is that a system can be decomposed into subsystems, and subsystems can be decomposed into lower level subsystems, and so on. Decomposition stops when a process box can be described with an Elementary Process Description using ordinary English, later on the process will be described more formally as a Function Description using, for example, pseudocode.
Balanced Data Flow Diagram set exists when the external data flows are equivalent from top to bottom levels.
Data Flow Diagram Symbols:
Bubble (Physical or Logical)- Depicts an entity or a process, in a logical data flow diagram, within which incoming data flows are transformed into outgoing data flows. These should be labeled with verbs.
Arrow- represents a pathway for data. These should be labeled with nouns indicating the data that is flowing, not the form or item.
Box- Represents a source or a destination of data outside the system.
Open-ended Rectangle- Represents a data store, such as a enterprise database, disk, filing cabinet, and so on.
Preparing Systems Documentation:
Table of Entities and Activities (describe the steps for creation):
The steps for creating a table of entities and activities are as follows:
1. Read the narrative, line by line, and circle each activity being performed (verbs).
2. For each of the activities, there must be an entity that performs the activity. Pur a box around the entity that performs the activity.
3. List (number) each activity in the order performed, regardless of the sequence noted in the narrative.
4. List the activity and the name of the entity that performs the activity.
5. Identify the inputs and outputs.
The table of entities and activities would look something like this: Entity Activity # Activity
Customer 1 Log on to Amazon web site
Documenting Information Systems:
This chapter introduces two techniques for documenting business processes- Data Flow Diagrams (DFD's) and System Flowcharting (SFC). It discusses how to read these documents, their purpose, and guidelines for creating DFD's and SFC's from narratives (see discussion)Data Flow Diagrams:
--graphical representation of a system--depicts a system's components, the data flows among the components, and the sources, destinations, and storage of data
http://spot.colorado.edu/~kozar/DFDtechnique.html This is a great page I found explaining DFD's
--here are some more web sites, which describe the elements of the DFD and the steps to drawing the DFD: http://www.compapp.dcu.ie/~renaat/ca2/ca214/ca214v.html http://www.stc.org/confproceed/2000/PDFs/00098.PDF
--Here is another one that describes the "layering" of DFD's graphically: http://www.umsl.edu/~sauter/analysis/dfd/dfd_intro.html
--Here is an example of the importance and practicality of DFD's in our society. This link shows the system process of Al-Qaida when planning the 9/11 attacks. It makes you think that if knowledge of the plot could have been found through this analysis, that maybe shutting down a link of this process could have prevented its occurrence.
Here is the PDF:
Types of Dataflow Diagrams (define and explain the differences):
- Logical Data Flow Diagram -- graphical representation of a system showing the systems processes, data stores, and the flows of data into and out of the processes and data stores
- Data Stores -- represent a place in the process where data comes to rest. A DFD does not say anything about the relative timing of the processes, so a data store might be a place to accumulate data over a year for the annual accounting process
- Logical DFD tells what activities are being accomplished but not ho
- Physical DFD - graphical represtantaion of a system showing the systems;s internal and external entities and the flows of data into and out of these entities - where, how and by whom - but not what activities are being accomplished
Physical DFD Vs Logical DFD- Physical DFD like the name says describes the physical components that perform the function where Logical explains what functions are being performed
- Physical DFD: System's infrastructure. Shows how the system will be implemented including the hardware, software, files, and people involved. It conatins information about the computerized system.
- Logical DFD: System's activities. Focuses on the business and how the business operates. It is not concerned with how the system will be constructed. It describes the business events that take place and the data required and produced by each event. It conatins information about the business.
-Here is a website that describes- Logical vs. Physical database modeling- http://www.developer.com/tech/article.php/641521Levels of Dataflow Diagrams:
Data Flow Diagram Symbols:
Preparing Systems Documentation:
Table of Entities and Activities (describe the steps for creation):
The steps for creating a table of entities and activities are as follows:1. Read the narrative, line by line, and circle each activity being performed (verbs).
2. For each of the activities, there must be an entity that performs the activity. Pur a box around the entity that performs the activity.
3. List (number) each activity in the order performed, regardless of the sequence noted in the narrative.
4. List the activity and the name of the entity that performs the activity.
5. Identify the inputs and outputs.
The table of entities and activities would look something like this:
Entity Activity # Activity
Customer 1 Log on to Amazon web site